Intellectual and developmental disabilities (IDDs) manifest as dysfunction in neural circuits. Thus, understanding and ultimately treating IDDs requires directly and precisely interfacing with neural circuits in animal models and the human brain. The goal of the Circuit Analysis & Modulation (CAM) Core is to provide a set of techniques and approaches for BCM IDDRC investigators, and the broader scientific community, which provide a path from hypothesis to pre-clinical readiness regarding neural circuit dysfunction in IDDs. The CAM Core is comprised of three sub-cores. The Tool Generation & Characterization sub-core will develop neurotropic viruses tailored to the particular needs of IDDRC neural circuit studies, and provide assistance applying the tools to their experiments. We will focus on lenti- and adeno-associated viral vectors that are engineered to drive gene expression in desired cell types. In particular, constructed viruses will allow investigators to target mainstay and emerging powerful optogenetic proteins to individual neurons, neuronal subsets, or desired lineages to suit their experimental design. These viral vectors afford the spatial and temporal flexibility of stereotaxic targeting, and provide a time- and cost-efficient alternative to transgenic mouse design. These tools provide valuable information about neuronal firing properties or patterns of connectivity, or provide a means to synthetically perturb function, facilitating study of normal circuit function or disease. The Circuit Assessment sub-core will provide assessment of sensory and neuromodulatory systems in mice and humans, both of which feature prominently in many IDDs. Prepulse inhibition (PPI) of acoustics startle is at the intersection of sensory and neuromodulatory functions, and PPI deficits are observed in many IDDs. We offer use of our novel human ?brain state and cognition? testing suite, which uses pupillometry to extract multiple indicators of neuromodulatory function in sensory recognition and sensorimotor gating, as well as an analogous high-throughput mouse system to IDDRC members. We also offer sophisticated attention tasks that tap into broader circuits, and two-photon imaging of circuit function in the PPI and attention tasks. The Circuit Modulation sub-core will perform in vivo neural recordings and targeted brain stimulation for IDDRC investigators. Combining optogenetic and chemogenetic methods with neurophysiological recordings allows testing circuit mechanisms with ground truth electrical readouts. In addition, targeted chronic deep brain stimulation has been increasingly applied to function- specific neuronal assemblies or pathways in preclinical studies of various neurological diseases, including IDDs. Thus we will provide assistance, design, and service towards testing targeted electrophysiological recordings or stimulation of nervous tissue in rodent models of IDD. In sum, the CAM core as a whole will provide powerful viral tools, electrical and optical recording and stimulation approaches, and cross-species non-invasive circuit assessment, in order to translate hypotheses about neural circuit dysfunction into pre-clinical readiness for IDD treatments.